Update Tango-derived icons to public domain
Created originally on Bitbucket by andrew_shadura (Andrej Shadura)
The icons derived from the Tango icon set are currently shipped under the terms of CC BY-SA 2.0 which is not fully compatible with DFSG which leads to extra work to replace them with fully free counterparts when e.g. packaging TortoiseHg for Debian.
Please update these icons to the latest versions which are in public domain.